The experimental data are compared to the results from the BnGa model [1]} and the MAID model [2]}.
The first is for double-pion production still restricted to the proton target. However, it fits also other reaction channels
for the proton and also some (e.g. single \(\pi ^0\)  production) for the neutron [3]}, [4]}, [5]}.
The MAID model tries to describe all isospin channels for double-pion production in the framework of an isobar model with
additional non-resonant backgrounds (e.g. Born terms) [2]}. This model was refit to all available data
for \(\gamma N\rightarrow \pi \pi N\)  including the new helicity decomposition for \(\gamma N\rightarrow \pi ^0\pi ^0 N\) .
